Method for Labelling a Substrate

ABSTRACT

The invention relates to a method for labelling a substrate, in which method at least one luminescent dye is deposited as a first identification feature in at least one transparent marker layer or in at least one functional layer on a surface of the substrate or on a layer which is situated on the surface, wherein the transparent marker layer or the functional layer is provided with a structure in a further step for producing a second identification feature by local destruction, in particular thermally. According to the invention, the deposition of the at least one marker layer or functional layer takes place by means of chemical gas-phase deposition using a flame or a plasma, by means of a sol-gel method or electrochemically.

The invention relates to a method for labeling a substrate according to the features of the preamble of claim 1.

Product piracy is a problem which gives rise to considerable economic damage to the manufactures of the original products, in particular in the case of high-value products (cosmetics, drugs, watches, lens spectacles, car windshields etc). In particular in the case of counterfeited drugs, the consumer is also seriously affected, since counterfeited drugs at best are ineffective and at worst can be harmful to health or even life-threatening. For such groups of products there is therefore a requirement for effective protection from copying.

The labeling of product packages, for example glass of a container or plastic packages, by laser printing have been known for a relatively long time. This type of labeling is easy to examine visually, but is also relatively easy to counterfeit.

In addition, addition of fluorescent dyes to polymers for production of apparatus housings and components is known. Using these dyes it is possible to set a defined color point or color value which can be read using a detector. Using differing colors, differing manufacturing time points are encoded.

WO 02/26507 A1 discloses a method and a device for personalizing luminescent authenticity features on data carriers of all types, in particular plastic cards. In a first process step, a luminescent authenticity feature is introduced into the card composite or applied to the card composite. In a second process step, the authenticity feature is personalized using a high-energy beam (e.g. a laser beam). In this process the intensity and/or wavelength of the beam is selected in such a manner that local bleaching of the structure of the authenticity feature takes place. As a result the structure of the authenticity feature is changed locally in such a manner that on luminescent illumination of the authenticity feature, the legend inscribed by personalization is recognizable as a negative image.

DE 10 2006 038 270 A1 describes a security and/or valuable document having a pattern of radiation modified components. The security and/or valuable document comprises a substrate and a print layer arranged on the substrate. First subregions of the document have a nonradiation-modified component or a slightly radiation-modified component. Second subregions of the document contain a radiation-modified component or a more strongly radiation-modified component, wherein the radiation-modified component only differs from the nonradiation-modified component by radiation-induced structural differences. The first subregions cannot be differentiated from the second subregions by the human eye. However, the first subregions can be differentiated from the second subregions using instrument-based measuring means.

DE 10 2005 025 095 A1 discloses a data carrier and a method for the production thereof. The data carrier, in particular a valuable document or security paper, comprises a substrate and a coating applied to the substrate into which labeling marks are introduced in the form of patterns, letters, numbers or images by the action of laser radiation. The coating contains a layer absorbing the laser radiation and a printing layer which is arranged above the absorbent layer and is at least partly pervious to the laser radiation. The printed substrate is compressed during or after the printing of the at least partly pervious layer.

The object of the invention is to specify a method for labeling a substrate, using which improved protection against copying is achieved.

The object is achieved according to the invention by a method having the features of claim 1.

Advantageous embodiments of the invention are subject matter of the subclaims.

In a method for labeling a substrate, which at least one luminescent dye is deposited as a first identification feature in at least one transparent marker layer or in at least one functional layer on a surface of the substrate or on a layer which is situated on the surface. The transparent marker layer or the functional layer is provided with a structure in a further step for generating a second identification feature by local destruction of the dye, in particular thermally.

According to the invention, the deposition of the at least one marker layer or functional layer takes place by means of chemical gas-phase deposition using a flame or a plasma, by means of a sol-gel method or electrochemically. A deposition process by means of chemical gas-phase deposition using a flame or a plasma is generally termed plasma activated chemical vapor deposition (PACVD). Processes of this type proceed not only at low pressure but also under atmospheric pressure conditions.

The first identification feature can encode a desired item of information on the chosen luminescent dye. Luminescent dyes emit light as a result of an external excitation, for example by irradiation with light of the visible spectrum, or in the ultraviolet range in the case of photoluminescence. Photoluminescent dyes are, in particular, phosphorescent and/or fluorescent. Both fluorescence and phosphorescence are forms of luminescence (cold light). Fluorescence ends relatively rapidly after the end of the irradiation (usually within a millionth of a second). In the case of phosphorescence, in contrast, post-illumination can occur over a period of fractions of a second to hours.

For generation of a second identification feature, the luminescent dye is locally destroyed. In this process, for example, one or more alphanumeric signs, symbols or logos or one- or two-dimensional barcodes are introduced into the dye-containing layer. The combination of the two features results in a particularly high security against counterfeiting.

Special luminescent dyes are invisible under the absence of UV radiation, or at low intensities, and accordingly do not impair the appearance of the product. Under such conditions, the second identification feature is likewise little identifiable in the luminescent layer. Not until the luminescent layer is excited, for example by irradiation with ultraviolet light, for example from a scanner, are both identification features visible. The scanner is then preferably designed so that it can not only make the identification features visible, but can also recognize them.

Alternatively to a luminescent dye, a dye switching thermochromically and/or electrochromically and/or photochromically and/or gasochromically can be deposited. Switching dyes change their color depending on a temperature (thermochromic), an electric field or a current flow (electrochromic), an excitation with light, in particular light of defined wavelengths (photochromic), or in the presence of a defined gas (gasochromic).

Likewise, nanozeolites loaded with the dye can be deposited. Nanozeolites are nanoscale particles of a varied family of chemically complex silicate minerals, zeolites. These minerals can store up to about 40 percent of their dry weight of water which is released again on heating. In moist air, the water can be absorbed without impairing the structure of the mineral. Zeolites are formed from a microporous frame-work structure of AlO₄ and SiO₄ tetrahedra. The aluminum and silicon atoms are bound to one another via oxygen atoms. This leads to a structure of uniform pores and/or channels in which substances can be adsorbed. Zeolites can therefore be used as sieves which adsorb only those molecules in the pores that have a kinetic diameter less than the pore openings in the zeolite structure. In the present case, the dyes are embedded in the pores of the nanozeolites.

In particular, organic fluorescent dyes are suitable, since these are temperature-sensitive and can readily be destroyed thermally.

The deposition by means of chemical gas-phase deposition using a flame or a plasma preferably takes place in such a manner that, from a working gas, a plasma jet or a flame is generated, wherein at least one precursor material is fed to the working gas and/or the plasma jet or the working gas and/or the flame and is brought to reaction in the plasma jet or the flame. On the substrate, at least one reaction product of at least one of the precursors is deposited as marker layer or functional layer. The dye is either dissolved or dispersed in a liquid medium, or is present in the nanozeolites. The dissolved or dispersed dye or the nanozeolites containing the dye are fed to the working gas or to the plasma jet or the flame separately or together with the precursor.

For dispersion, organic dyes are preferably used, in particular organic dyes which are more chemically stable. The disposed dye is preferably fed into the working gas, the flame or the plasma jet by means of a peristaltic pump.

In the case of the sol-gel coating, a precursor is dissolved in a solvent and admixed with a catalyst, for example an acid. This sol is applied to the surface that is to be coated and dried, in such a manner that the crosslinking begins. The resultant network is termed a gel. After the drying, the layer can be tempered, wherein the layer is completely crosslinked. A temperature for tempering the layer is preferably chosen depending on the decomposition temperature of the dye, i.e. to be lower than the decomposition temperature, in order not to destroy the dye during the tempering. For example, the tempering of the layer takes place at a temperature of at least 300° C. The layer thus produced is mechanically stable.

The deposition of at least one further marker layer or functional layer preferably takes place by chemical gas-phase deposition using a flame or a plasma, by means of sol-gel method, or electrochemically.

The sol-gel coating can be arranged downstream of a previously chemical gas-phase deposition from the flame or the plasma.

Particularly preferably, the deposition by means of chemical gas-phase deposition using a flame or a plasma is carried out at atmospheric pressure, in particular as an atmospheric pressure plasma method. By operating at atmospheric pressure, particularly advantageously, a time-consuming process step for evacuation of a process chamber and also equipment for vacuum generation such as vacuum pumps and process chamber are spared. As a result, the method may be integrated without great expenditure into a process chain that comprises production and hardening of the substrate.

The local destruction takes place by thermal introduction into the luminescent dye-containing layer. Via the heat input, the temperature in a locally restricted region is elevated over the decomposition temperature of the luminescence dye and the luminescence property is destroyed in a locally restricted manner. That is to say, via the locally restricted energy input, in particular the heat input, a decomposition energy for decomposition of the luminescent dye is reached or exceeded, as a result of which the luminescence property is destroyed in a locally restricted manner.

The local destruction is preferably performed by means of a laser. This simplifies the labeling, since the laser is usually used anyway for printing or engraving. With the aid of the laser, pinpoint-accurate thermal destruction of the dyes is possible. The laser can be focused in such a manner that the dye in the marker layer or functional layer can be destroyed even when one or more further layers are situated thereabove which were deposited later, without these further layers being damaged. If necessary, the laser can be tuned to an absorption wavelength of the respective dye.

Likewise, the local destruction can take place by means of a flame or a plasma. Atmospheric pressure plasma jets are particularly suitable therefor, which can be positioned locally to a high resolution.

Likewise, the local destruction can take place by means of a plasma microstamp. For this purpose plasma sources are used in which, in cavities, which are formed temporarily between a print mold (stamp or roller) and the surface of the coated substrate, what are termed cold discharges ignite. These treat the surface locally. These discharges are dielectric barrier discharges and high-frequency discharges.

The luminescent dye used is preferably a fluorescent dye, in particular an organic fluorescent dye, since this can be destroyed particularly readily by heating. Preferably, a fluorescent dye is used which only emits light when it is excited by an assistant such a UV light and is otherwise invisible.

In a preferred embodiment, a transparent or translucent substrate, in particular an optical glass, for example a lens, in particular a spectacle lens, is labeled with the first and second identification features at a locally restricted site of the substrate.

In a further preferred embodiment, a transparent or translucent substrate, for example a watch glass or a car windshield, is labeled with the first and second identification features at a locally restricted site of the substrate.

In a particularly preferred embodiment, a transparent or translucent substrate, in particular a container, is labeled by the first and second identification features. The substrate can consist, for example, of glass or a transparent plastic.

In this case the deposition of the marker layer or of the functional layer can take place at the end of a process for producing the container, for example at the location of a manufacturer of the container. The local destruction can then take place in a process for charging the container, that is to say not necessarily at the manufacture of the container, but at the manufacture of a product that is charged into the container.

The first identification feature is used, for example, by means of selection of the luminescent dye, for coding a production batch or a production date of the container. Differing colors of the luminescent dye can encode, for example, differing production batches. By means of the second identification feature, a product batch or a filling date of a product charged into the container can then be encoded. This permits the production chain to be kept track of.

The marking of the container with the identification features can take place, for example, on the bottom or on the walls of the vessel.

Exemplary embodiments of the invention will be described in more detail hereinafter.

Using an atmospheric-pressure plasma, a silicon dioxide layer was applied as a marker layer to a substrate made of glass. The result of this plasma activated chemical vapor deposition process (PACVD process) was a layer having a thickness of about 200 nm. By adding a mist containing a fluorescent dye to the plasma jet, particles of this dye were incorporated into the matrix of the marker layer.

The silicon dioxide coating by means of atmospheric pressure plasma took place using an organosilicon precursor, for example hexamethyldisiloxane (HMDSO). The plasma torch was operated at a power of 350 W. The substrate was moved at a process speed of 100 mm/s to 200 mm/s at a distance of 10 mm from the torch. The plasma torch was moved over the substrate in a meandering shape, and the raster spacing was 3 mm. The fluorescent dye chosen was Blue-Violet LC-Fluorescent Dye 1 from Synthon Chemicals GmbH & Co. KG.

The substrate thus coated was irradiated with a laser, wherein the laser was moved in a raster scan across the surface of the substrate. As a consequence, the fluorescence activity of the layer was destroyed locally in the region raster-scanned by the laser. In this case a CO₂ laser of wavelength 10.6 μm having a focal length of 200 mm, a focus diameter of 300 μm and a power of 18.5 W was used.

It is possible to deposit a different dye, in particular a luminescent dye, and/or a thermochromically and/or electrochromically and/or photochromically and/or gasochromically switching dye, as the first identification feature in the marker layer, or in a functional layer.

The second identification feature can be destroyed by other means, in particular thermally. For example, for this purpose, a flame or a plasma, in particular a plasma microstamp, can be used.

Likewise, nanozeolites loaded with the dye can be deposited in the marker layer or functional layer.

The deposition can take place as an alternative to the atmospheric pressure plasma method using other methods, for example by means of chemical gas-phase deposition, using a flame, by means of a sol-gel method or by means of electrochemical deposition.

The sol-gel coating can be connected downstream of a previous chemical gas-phase deposition from the flame or the plasma. 

1. A method for labeling a substrate in which at least one luminescent dye is deposited as a first identification feature in at least one transparent marker layer or in at least one functional layer on a surface of the substrate or on a layer which is situated on the surface, wherein the transparent marker layer or the functional layer is provided with a structure in a further step for generating a second identification feature by local destruction, in particular thermally, characterized in that the deposition of the at least one marker layer or functional layer takes place by means of chemical gas-phase deposition using a flame or a plasma, by means of a sol-gel method or electrochemically.
 2. The method as claimed in claim 1, characterized in that the deposition of at least one further marker layer or functional layer takes place by chemical gas-phase deposition using a flame or a plasma, by means of sol-gel method, or electrochemically. 3.-9. (canceled)
 10. The method as claimed in claim 1, characterized in that the deposition takes place by means of chemical gas-phase deposition using a flame or a plasma under atmospheric pressure.
 11. The method as claimed in claim 2, characterized in that the deposition takes place by means of chemical gas-phase deposition using a flame or a plasma under atmospheric pressure.
 12. The method as claimed in claim 1, characterized in that the local destruction takes place by means of a laser, a flame or a plasma, wherein, via the heat input, the temperature in a locally restricted region is elevated over the decomposition temperature of the luminescent dye and the luminescence property is destroyed in a locally restricted manner.
 13. The method as claimed in claim 2, characterized in that the local destruction takes place by means of a laser, a flame or a plasma, wherein, via the heat input, the temperature in a locally restricted region is elevated over the decomposition temperature of the luminescent dye and the luminescence property is destroyed in a locally restricted manner.
 14. The method as claimed in claim 10, characterized in that the local destruction takes place by means of a laser, a flame or a plasma, wherein, via the heat input, the temperature in a locally restricted region is elevated over the decomposition temperature of the luminescent dye and the luminescence property is destroyed in a locally restricted manner.
 15. The method as claimed in claim 11, characterized in that the local destruction takes place by means of a laser, a flame or a plasma, wherein, via the heat input, the temperature in a locally restricted region is elevated over the decomposition temperature of the luminescent dye and the luminescence property is destroyed in a locally restricted manner.
 16. The method as claimed in claim 12, characterized in that the local destruction takes place by means of a plasma microstamp.
 17. The method as claimed in claim 13, characterized in that the local destruction takes place by means of a plasma microstamp.
 18. The method as claimed in claim 14, characterized in that the local destruction takes place by means of a plasma microstamp.
 19. The method as claimed in claim 15, characterized in that the local destruction takes place by means of a plasma microstamp.
 20. The method as claimed in claim 1, characterized in that the luminescent dye used is a fluorescent dye.
 21. The method as claimed in claim 2, characterized in that the luminescent dye used is a fluorescent dye.
 22. The method as claimed in claim 1, characterized in that a transparent or translucent substrate, in particular a container, is labeled.
 23. The method as claimed in claim 2, characterized in that a transparent or translucent substrate, in particular a container, is labeled.
 24. The method as claimed in claim 20, characterized in that the deposition of the marker layer or of the functional layer takes place at the end of a process for producing the container and the local destruction takes place in a process for filling the container.
 25. The method as claimed in claim 21, characterized in that the deposition of the marker layer or of the functional layer takes place at the end of a process for producing the container and the local destruction takes place in a process for filling the container.
 26. The method as claimed in claim 22, characterized in that the first identification feature is used by selection of the luminescent dye for coding a production batch or a production date of the container, and a product batch or a filling date of a product charged into the container is encoded by means of the second identification feature.
 27. The method as claimed in claim 23, characterized in that the first identification feature is used by selection of the luminescent dye for coding a production batch or a production date of the container, and a product batch or a filling date of a product charged into the container is encoded by means of the second identification feature. 